Flexible contaminant-resistant grout composition and method

Abstract

A flexible grout composition and method of disposing the composition in position, in contact with an earthen formation, such as a coating on a trench wall, or within a bore hole, for example to cement a conduit within the bore hole to prevent fluid loss, for sealing and grouting well casings, plugging abandoned wells, and waterproofing earthen structures, particularly in environments where the grout composition is in contact with contaminated water. The flexible grout composition includes a water-swellable clay, such as sodium bentonite; an optional solid particulate filler, such as an essentially nonswellable bentonite clay, such as calcium bentonite, herein defined as a bentonite clay having calcium as the predominant exchangeable cation; a water-soluble polymer; and an optional dispersing agent, such as sodium acid pyrophosphate (SAPP).

What is claimed is: 
     
       1. A method of protecting a structure against penetration by contaminated water comprising mixing a thixotropic slurry composition comprising: about 15% to about 85% water;   about 7% to about 60% water-swellable sodium bentonite clay, said sodium bentonite clay comprising about 25% to about 100% by weight of the slurry, based on the dry weight of water-insoluble solids in the slurry;   about 4% to about 35% solid, essentially non water-swellable particulate filler; and   about 0.001% to about 8% of a water-soluble polymer; and pumping the composition, while in slurry form, to dispose the composition in contact with the structure so that the composition sets in contact with the structure, while maintaining flexibility of the composition after complete curing of the composition.     
     
     
       2. The method of claim 1, wherein the structure comprises a conduit disposed within a drill hole and wherein the composition in slurry form is pumped into an annular space defined between the conduit and an earthen formation formed by the drill hole, to cement the conduit into position within the drill hole. 
     
     
       3. The method of claim 1, wherein the structures comprises a conduit disposed within an abandoned drill hole, and the conduit is cemented in position with said composition to prevent the conduit from collapsing. 
     
     
       4. The method of claim 1, wherein the structure comprises an excavated trench wall. 
     
     
       5. The method of claim 1, wherein the sodium bentonite clay has a dry particle size less than about 300 μm. 
     
     
       6. The method of claim 5, wherein the sodium bentonite clay has a dry particle size less than about 200 μm. 
     
     
       7. The method of claim 6, wherein the sodium bentonite clay has a dry particle size less than about 75 μm. 
     
     
       8. A method of protecting a structure against penetration by contaminated water comprising mixing a slurry comprising: about 15% to about 85% water;   about 7% to about 60% water-swellable sodium bentonite clay;   about 4% to about 35% solid, essentially non water-swellable particulate filler; and   about 0.001% to about 8% of a water-soluble polymer; pumping the composition, while in slurry form, to dispose the composition in contact with the structure so that the composition sets in contact with the structure, while maintaining flexibility of the composition after complete curing of the composition; and     wherein the sodium bentonite is rewetted to a moisture content of about 15% to about 45%, based on the dry weight of the sodium bentonite clay, and impregnated with dissolved polymer, extruded, dried to a moisture content less than about 12% by weight and then ground to a particle size less than about 75 μm.   
     
     
       9. A method of protecting a structure against penetration by contaminated water comprising mixing a slurry comprising: about 15% to about 85% water;   about 7% to about 60% water-swellable sodium bentonite clay;   about 4% to about 35% solid, essentially non water-swellable particulate filler; and   about 0.001% to about 8% of a water-soluble polymer; pumping the composition, while in slurry form, to dispose the composition in contact with the structure so that the composition sets in contact with the structure, while maintaining flexibility of the composition after complete curing of the composition; and     wherein the sodium bentonite is rewetted to a moisture content of about 15% to about 45%, based on the dry weight of the sodium bentonite clay, and impregnated with dissolved polymer, extruded, dried to a moisture content less than about 12% by weight and then ground to a particle size less than about 300 μm.   
     
     
       10. The method of claim 8, wherein the sodium bentonite clay is impregnated with 0.01% to about 10% by weight of said water-soluble polymer, based on the dry weight of sodium bentonite clay. 
     
     
       11. The method of claim 8, wherein the sodium bentonite clay is impregnated with at least about 1% by weight of said water-soluble polymer, based on the dry weight of sodium bentonite clay. 
     
     
       12. The method of claim 11, wherein the sodium bentonite clay is impregnated with dissolved polymer in an amount of about 1% to about 2% by weight, based on the dry weight of the sodium bentonite clay. 
     
     
       13. In a method of protecting a structure against penetration by contaminated water comprising mixing a thixotropic slurry composition and pumping the composition, while in slurry form, to dispose the composition in contact with the structure so that the composition sets in contact with the structure, while maintaining flexibility of the composition after complete curing of the composition, the improvement comprising: homogeneously mixing a composition comprising a water-swellable sodium bentonite clay, dried to moisture content of 12% by weight or less, in an amount of about 25% to about 100% by weight of water-insoluble solids in the composition, together with a water-soluble polymer, in an amount of about 0.01% to about 10% by weight, based on the weight of bentonite clay solids in the composition;   rewetting the sodium bentonite clay with water to a moisture content of more than about 12% by weight, and impregnating the clay with water-dissolved polymer;   redrying the clay to a moisture content less than about 12% by weight, based on the dry weight of the clay; and   mixing the redried clay and polymer with water to form said thixotropic slurry composition.   
     
     
       14. In the improved method of claim 13, further including impregnating the sodium bentonite clay with at least about 1% polymer, based on the dry weight of the sodium bentonite clay. 
     
     
       15. In the improved method of claim 13, further including impregnating the sodium bentonite clay with about 1% to about 2% polymer, based on the dry weight of the sodium bentonite clay. 
     
     
       16. In the improved method of claim 13, wherein the sodium bentonite clay is rewetted to a moisture content of at least about 15% by weight. 
     
     
       17. In the improved method of claim 16, wherein the sodium bentonite clay is rewetted to a moisture content of about 18% to about 100% by weight, based on the weight of the dry sodium bentonite clay. 
     
     
       18. In the improved method of claim 13, further including adding a dispersing agent together with the sodium bentonite clay and water-soluble polymer such that the rewetting step impregnates the clay with water and dispersing agent. 
     
     
       19. In the improved method of claim 18, wherein the dispersing agent for the sodium bentonite clay is included in the composition in an amount of about 0.05% to about 15%, based on the dry weight of water-insoluble solids in the composition. 
     
     
       20. In the improved method of claim 19, wherein the dispersing agent is selected from the group consisting of sodium acid pyrophosphate; tetra sodium acid pyrophosphate; sodium meta phosphate; sodium tetra phosphate; tannic acid; sodium tannate; soda ash; caustic soda; calcium lignosulfonate; lignin; chrome lignosulfonate; and mixtures thereof. 
     
     
       21. In the improved method of claim 13, further including adding calcium bentonite clay with said sodium bentonite clay and water-soluble polymer, in an amount of about 25% to about 45% by weight, based on the weight of water-insoluble solids in the composition. 
     
     
       22. In the improved method of claim 13 further including the steps of: grinding the redried, polymer-impregnated sodium bentonite clay;   recovering finely ground particles, having a particle size less than 300 μm; and   adding said finely ground sodium bentonite particles, in an amount of about 1% to about 100% by weight of polymer-impregnated sodium bentonite clay in the composition, with water to form said thixotropic slurry composition.   
     
     
       23. In the improved method of claim 13, wherein the thixotropic slurry composition includes about 15% to about 85% water. 
     
     
       24. In the improved method of claim 23, wherein the thixotropic slurry composition includes about 25% to about 85% water. 
     
     
       25. In the improved method of claim 23, wherein the thixotropic slurry composition includes about 15% to about 45% water. 
     
     
       26. In the improved method of claim 25, further including the step of extruding the composition through a die opening, after rewetting and prior to redrying, to impregnate the sodium bentonite clay with water-dissolved polymer. 
     
     
       27. In the method of claim 26, further including adding calcium bentonite clay to said sodium bentonite clay and water-soluble polymer, such that the rewetted composition includes about 25% to about 45% calcium bentonite clay, based on the weight of water-insoluble solids in the composition, prior to extruding.